Stamps and stamp pads have been commonly used to easily transfer and reproduce letters, symbols, and graphics by imprinting. Stamps pads typically consist of a single color, such as black, blue, or red, and are primarily used for office applications.
In contrast to such single-color stamp pads, multi-color stamp pads comprising a number of ink pads with different colors arranged in a line have become commercially available in recent years. FIG. 11 depicts a schematic cross-sectional view of such a conventional multi-color stamp pad. As shown in FIG. 11, the conventional multi-color stamp pad comprises a depression 22 formed in base 21. The depression 22 has adhered thereto in a line a plurality of colored ink pads 23. The ink pads 23 each comprise a different color. The ink pads 23 are made by absorbing liquid pigment-based inks of a certain viscosity and thixotropy into sponges 20. The ink pads 23 are typically fastened so that their tops protrude from the base 21. The ink pads 23 are covered by a lid 24. In addition, a groove 25 is typically formed around the base 21 so that the perimeter of the lid 24 can be inserted into the groove 25, thereby closing the lid on the base in an easily attachable and detachable manner.
The multi-color stamp pad is then used to transfer the multitude of inks to a rubber stamp in a rainbow of colors, which colors can then be transferred to an appropriate substrate, such as paper, to provide an imprinted image consisting of a variety of different colors.
The conventional multicolor stamp pads are limited, however, to certain liquid pigment-based inks because such inks will not disperse from one ink pad to another even if adjacent ink pads touch each other directly, so the differently colored inks do not mix together. Thus, sharp lines are maintained between the inks, and there is no concern with the creation of undesirable colors at the junction of adjacent pads, even if the pads are in actual contact.
The use of aqueous dye-based inks in such conventional multi-color stamp pads has been problematic because such inks will disperse from one ink pad to another when adjacent ink pads are in contact with one another. As time passes, the movement of the ink between ink pads causes the colors of the ink pads to change. As a result, the original colors cannot be maintained. Additionally, unattractive color combinations may result at the junctions between the ink pads.
In the past, when such aqueous dye-based inks were used in a single stamp pad, the adjacent ink pads were separated from each other by various methods. For example, as shown in FIG. 12, the individual ink pads 23 of the multi-colored stamp pad were partitioned by a plastic partitioning plate 26. The plastic partitioning plate prevented the inks from mixing with each other. When the ink pads were to be used, the plastic partitioning plate would be removed. With this method, however, removing the plastic partitioning plate was bothersome, requiring careful manipulation by the fingers of the user, and also created a possibility of smearing ink from the plate onto a non-desired surface, such as clothing. In addition, after the plastic partitioning plate was removed, spaces remained between the colored ink pads. This was problematic because no ink (and therefore no color) was then applied at these spaces to a rubber stamp applied to the pad, and therefore the image imprinted by the rubber stamp had incomplete areas.
In an alternative previous approach, conventional multi-color stamp pads incorporating aqueous dye-based inks having two colors placed the differently colored ink pads in small separate containers. The two separate containers were housed in a stamp pad base, and the individual colored ink pads were partitioned from each other by the walls of the containers. This method was problematic, however, because multi-color stamp images could not be imprinted to the paper because the partitioning walls of the small containers projected above the surface of the ink pads, thereby preventing the stamp from simultaneously contacting two differently colored ink pads. Additionally, only a small number of colored ink pads (i.e., two) were housed in the stamp holder.
Accordingly, there has gone unmet a need for a stamp pad permitting the use of multiple, preferably more than two, aqueous dye-based inks of different colors. Further, there has gone unmet a need for such a pad comprising multiple aqueous dye-based inks wherein the ink does not disperse from one area of the stamp pad to another, and therefore wherein the inks of the stamp pad are maintained in a desired, sharply defined area. There has also gone unmet a need for a stamp pad permitting the use of multiple aqueous dye-based inks wherein upon transferring ink from the stamp pad to the rubber stamp (and later to an appropriate substrate such as paper), the ink is applied to all desired surfaces of the rubber stamp, with no "uninked" areas between the various colors.
In addition, there has gone unmet a need for a multi-color stamp pad that, when not in use, does not permit dispersion of the differently colored inks from one area to another within the pad. The present invention provides these and other related advantages.